1. Field of the Invention
The present invention relates to an electronic flash device for a camera. More particularly, the present invention relates to an electronic flash device for a camera in which flash light can be effectively applied to a photographic subject located at a very near distance in closeup photography.
2. Description Related to the Prior Art
There are various types of commercially available cameras. Many types of cameras incorporate an automatic focus changing mechanism and an automatic exposure adjusting mechanism for automated focusing and adjustment of exposure. Some flash-built-in type of camera is provided with an automatic light adjustor, which adjusts an emitted amount of flash light automatically according to a photographic subject distance and photographic subject brightness For flash photography of a photographic subject at a very near distance with such a camera, an aperture stop is stopped down, or an emitted amount of the flash light is reduced, to optimize exposure of the photographic subject.
If the camera is a low-cost type without the automatic exposure adjusting mechanism or the automatic light adjustor, the subject brightness is excessive if flash light is emitted at the very near distance, to result in an over-exposure photograph. Distribution of the flash light is predetermined for illumination to a photographic field at a normally used range of a subject distance in flash photography. If the photographic subject is located at a nearer distance than this normally used range, a central portion of one frame is illuminated considerably by the flash light, to create a great difference in the emitted light amount from peripheral portion of the frame. As a result, a photographic print is likely to have the excessively white central portion.
JP-A 9-138456 discloses an adapter attachable to the camera for a good condition of closeup photography even if the camera does not have the automatic exposure adjusting mechanism or the automatic light adjustor. In the document, an auxiliary lens is disposed in the adapter for changing a focal point to a position offset in the direction of the near distance from an initial focal point. The auxiliary lens is fixedly disposed in front of a taking lens of the camera, to enable the closeup photography of the photographic subject at the very near distance. Also the adapter is provided with a light reducing plate, which includes a light-shielding flat plate and a number of holes formed therein for passing of the flash light. For the closeup photography, a flash emitting component of the flash device is associated with the light reducing plate set in front thereof for restrict the amount of the flash light to be applied to the photographic subject. Note that the holes for passing of the flash light have a size and arrangement each determined in consideration of the emitted amount and distribution of the flash light emitted from the flash emitting component.
In the light reducing plate, there are formed a great number of holes for passing of the flash light. If a great amount of the flash light is emitted from the flash emitting component, the holes do not effectively operate for light reduction. The holes are very close to one another, so that fluxes of the flash light through the holes are overlapped on one another at the photographic subject at the very near distance. There occur bright and dark portions of photographic subject distinct apparently from one another. Differences between the bright and dark portions are so conspicuous according to greatness of the amount of the flash light, to lower evenness in the illumination.
Furthermore the light reducing plate of the prior art has a size totally covering the flash emitting component. If the light reducing plate is incorporated in the camera, a large space in the camera is required for retreat of the light reducing plate from the flash emitting component. There occurs unwanted enlargement of the camera.